The brain is an extremely complex structure, having on the order of a trillion neurons. Each neuron has multiple hundreds or thousands of connections or synapses to the other neurons. Studying the brain includes determining how these connections operate.
It has recently been suggested that neural information processing is the result of collective activity in large ensembles of neurons. This can be studied by neural cell cultures.
Microelectrodes are the standard tool. However, microelectrodes typically allow recording signals from only a few cells at any one given time. Each electrode requires a micromanipulator. Impaling the cells is a tedious and invasive procedure.
It is possible to record neural activity optically, by monitoring the fluorescence (or absorption) of neurons stained with voltage-sensitive dyes. These potentiometric probes sense the voltage across the cell membrane, which changes from about 60 mV to about +40 mV during an action potentialxe2x80x94the signal that causes neurotransmitters to be released at the synapse. By shifting the charge on a dye molecule in the membrane, the electric field changes the optical properties of the dye. This process occurs much faster than the voltage transient of an action potential, which is typically a few milliseconds (ms) in vertebrate neurons. Unfortunately, the change in fluorescence during an action potential is only a couple percent of the resting fluorescence level, per 100 mV change in membrane potential. This, and the rapidity with which neural signals come and go, has made optical recording of neural activity a daunting task.
Photodiodes have often been the way of choice to study voltage-sensitive dyes. Photodiodes and other image sensors output an analog signal, which is usually converted to digital for study. If an nxm array of photodiodes is provided, the entire nxm array of pixels needs to be digitized. This requires nxm conversion cycles.
Speed of the analog to digital converter hardware is important. However, the cost of the A/D converter hardware increases substantially at higher speeds.
The present system teaches a new way of measuring/monitoring changes in a small area using a Charge Coupled Device (xe2x80x9cCCDxe2x80x9d) system. The CCD system is controlled by a special control system that allows obtaining greater resolution and individual pixel imaging.
According to the present system, a CCD camera is disclosed. This CCD camera is capable of producing animations at very high frame. The custom user-interface allows the user to select only the pixels of interest. By so doing, relatively slower components can be used while obtaining a higher throughput for the image, e.g. over 1000 frames per second.